Production of 2-methyl-2-hepten-6-one

ABSTRACT

The production of 2-methyl-1-hepten-6-ones (important for organic syntheses of perfumes and carotenoids) by isomerization of 2-methyl-1-hepten-6-one by means of finelly divided palladium or compounds of divalent palladium as isomerization catalysts.

United States Patent Mueller et al. [4 1 June 13, 1972 [541 PRODUCTIONOF 2-METHYL-2- 1,267,682 5/1968 Germany ..260/593 R HEPTEN-6-ONE OTHERPUBLICATIONS [72] lnventors: Herbert Mueller, Frankenthal/ U pper P l iHarald m; Horst pommer, Meinwald et al., J. Amer. Chem. Soc." Vol. 80,pp. 5266- both of Ludwigshafen/Rhine, all of 5270- Germany PrimaryExaminer-Bemard Helfin [73] Ass1gnee: Badische Anl1in-& SodaFabrlkAktien- Assistant 5 Lone gesenschafl Ludmgshafen/Rhme, Anomey-Johnston,Root, OKeefe, Keil, Thompson & Shunmany [22] Filed: Sept. 20, 1968 [57]ABSTRACT 21 Appl. No.: 761,328

The production of 2-methyl-l-hepten-6-ones (important for organicsyntheses of perfumes and carotenoids) by isomeriza- [52] U.S. Cl.260/593 on f 2 by means f fi fl divided Cl 49/20 palladium or compoundsof divalent palladium as isomeriza- [58] Field of Search ..260/593, 593R ion catalyst,

[56] References Cited 9 Claims, No Drawings FOREIGN PATENTS ORAPPLICATIONS 1,112,731 8/1961 Germany 260/593 R PRODUCTION OF2-METHYL-2-HEPTEN-6-ONE The present invention relates to a new processfor the production of 2-methyl-2-hepten-6-one (I).

It is generally known that olefinically unsaturated carbonyl compoundscan be isomerized by displacement of the C C double bonds using variouscompounds having catalytic activity or by thermal treatment.

Attempts made hitherto to isomerize 2-methyl-l-hepten-6- one (11) into2-methyl-2-hepten-6-one (l) have proved to be very unsatisfactorybecause of numerous secondary reactions. Thus for example in theisomerization of (II) with sulfuric acid, mainly carbocyclic compoundsare obtained instead of (1) (cf. Journal of the American ChemicalSociety, 80 (1958, page 5,266).

It is therefore the object of the present invention to make 2-methyl-2-hepten-6-one (I) more easily accessible than hitherto.

We have now found that 2-methyl-l-hepten-6-one can unexpectedly beisomerized in outstanding yields by using as the isomerization catalystfor the purpose finely divided metallic palladium or a compound ofdivalent palladium.

The palladium may be in the form known as palladium black or as aprecipitate or carrier substances such as active carbon, barium sulfateor silica gel.

Palladium (ll) oxide and the halides such as the fluoride, chloride,bromide and iodide are particularly suitable as compounds of divalentpalladium. Complexes of the halides with zerovalent ligands andparticularly those containing basic N or P atoms in the molecule are,however, also suitable. Examples of such ligands are a,a, dipyridyl,benzonitrile and triphenylphosphine.

The amount of palladium or palladium( II) compound required is generallyfrom 0.01 to 5% by weight, preferably 0.1 to 2% by weight, withreference to the amount of (II). It is possible to use larger or smalleramounts of catalyst, however, in which case the isomerization isaccelerated or retarded.

The reaction may be carried out at temperatures of 100 to 250 C,preferably from 150 to 200 C, at atmospheric or superatmosphericpressure, for example up to 50 atmospheres, with or without solvent,batchwise or continuously.

Hydrocarbons which are liquid under the reaction conditions concerned,for example hexane, heptane, petroleum ether, petrol, benzene, tolueneor xylene, are particularly suitable as solvents; ethers such asdiphenyl ether, 2,2dimethoxy diethyl ether and 2,2'-diethoxy diethylether may also be used.

After the isomerization is over, the reaction mixture may be worked upas usual, preferably by distillation.

The product (I) of the process is a valuable intermediate for organicsyntheses, particularly for the production of compounds of thecarotenoid series and perfumes.

The invention is illustrated by the following Examples.

EXAMPLE 1 1 g of palladium black is added to g ofZ-methyl-l-hepten-6-one, the mixture is heated for 6 hours at 160 C atatmospheric pressure and worked up in the conventional manner.

Pure 2-methyl-2-hepten-6-one is obtained in a 96.5% yield. It has aboiling point of 171 C at 760 ton; n 1.4387.

EXAMPLE 2 1 g of palladium(ll) chloride is added to 100 g of 2-methyl-1-hepten-6-one, the mixture is heated for 4 hours at atmosphericpressure at C and then worked up in the usual way.

Pure 2-methyl-2-hepten-6-one is obtained in an 81.4% yield.

We claim:

1. A process for the production of 2-methyl-2-hepten-6-one whichcomprises isomerizing 2-methyl-1-hepten-6one by means of finely dividedmetallic palladium or a compound of divalent alladium selected from theoup consisting of palladium (ll) oxide, palladium (ll) hali e, a complexof a palladium halide with a,a-dipyridyl as a zerovalent ligand, acomplex of a palladium halide with benzonitrile as a zerovalent ligandand a complex of a palladium halide with triphenylphosphine as azerovalent ligand as an isomerization catalyst at a temperature of from100 to 250 C.

2. A process as in claim 1, wherein said catalyst is palladium black.

3. A process as in claim 1, wherein said catalyst is a palladium(ll)halide.

4. A process as in claim 1, wherein said catalyst is palladium( 11)oxide.

5. A process as in claim 1, wherein said catalyst is palladium(ll)chloride.

6. A process as in claim 1, wherein the amount of catalyst used is 0.01to 5% by weight with reference to the amount of 2-methyl-1-hepten-6-one.

7. A process as in claim 1, wherein the amount of catalyst used is 0.1to 2% by weight with reference to the amount of 2- methyl- 1-hepten6-one.

8. A process as in claim 1, wherein the temperature is from 150 to 200C.

9. A process as in claim 1, wherein said isomerization is carried out ina hydrocarbon which is liquid under the reaction conditions.

UNITED STATES PATENT OFFICE 4 CETIFICATE or c ten Patent No. 3, 7 DatedJune 15., 1972 Herbert Mueller, Harald Koehl, and Horst Pommer It iscertified that: error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown'below:

First page, left-hand column, "Upper Palati'nate" should readfalzleft-hand column, insert v 50 1 Foreign Application Priority Data ISeptember 22, 1967* Germany. .P 12 67 682.3

Column 1, line 5, "c c" should read :c

Signed and sealed this 19th day of' December 1972,

(SEAL) Attest:

ROBERT GQTTSCHALK Commissioner of Patents EDWARD M.FLE-TCHER, JR.Attesting Officer

2. A process as in claim 1, wherein said catalyst is palladium black. 3.A process as in claim 1, wherein said catalyst is a palladium(II)halide.
 4. A process as in claim 1, wherein said catalyst ispalladium(II) oxide.
 5. A process as in claim 1, wherein said catalystis palladium(II) chloride.
 6. A process as in claim 1, wherein theamount of catalyst used is 0.01 to 5% by weight with reference to theamount of 2-methyl-1-hepten-6-one.
 7. A process as in claim 1, whereinthe amount of catalyst used is 0.1 to 2% by weight with reference to theamount of 2-methyl-1-hepten-6-one.
 8. A process as in claim 1, whereinthe temperature is from 150* to 200* C.
 9. A process as in claim 1,wherein said isomerization is carried out in a hydrocarbon which isliquid under the reaction conditions.